HIV disease is becoming more of a chronic condition in countries with good access to medical care. In the area of NeuroAIDS there is no acknowledged, useful biomarker for the cognitive disorder associated with HIV disease (i.e., HIV-Associated Neurocognitive Disorder (HAND)), independent of the cognitive tests. Magnetic resonance imaging and positron emission tomography have been tried, but have yet to fulfill their promise {Price, 2007 #6509}. One emerging technology that has only recently been applied to HIV Disease - by our research team - is magnetoencephalography (MEG). MEG is a non-invasive technique for measuring neuronal activity by recording the magnetic fields induced by synchronized neuronal currents. MEG has the highest spatial and temporal resolution of any current neuroimaging technology, and is used most commonly in the clinical evaluation of patients with seizure disorders, and by cognitive neuroscientists to investigate electrophysiological responses of the CNS. Unlike techniques such as functional MRI, MEG does not rely on the blood-oxygen level dependent response in order to generate responses. Thus, it will be very important to determine whether MEG can identify abnormal brain function in HIV Disease - especially when cognitive dysfunction is mild and not yet affecting activities of daily living. Our team has demonstrated that we can differentiate infected from uninfected study subjects, that there may be an independent MEG-derived variable that is sensitive to cognitive dysfunction, and that MEG signals are stable over a 6-month period. The preliminary research was conducted in the context of an R03-funded study, so the overall goal of this new R21 research project is to obtain the necessary additional data from 30 infected individuals (and 10 controls) to finalize the design for a larger, longitudinal study. These data will allow us to begi to characterize the neurocognitive outcomes of HIV Disease using a highly sensitive electrophysiological tool.